JP2012073458A - Optical scanner and image forming apparatus equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner which prevents the lowering of rigidity in the vicinity of an opening formed on the base of a housing, suppresses the vibration of optical components arranged in the base, and can prevent deterioration in image quality.SOLUTION: The optical scanner 13 has a housing 25 that has the inside thereof vertically partitioned by a base 25A and houses optical components such as at least a light source, a polygon mirror (deflector) 26 for deflecting the light beam emitted from the light source, first imaging lenses 32 and 42 and second imaging lenses 33 and 43 for converting the light beam deflected by the polygon mirror 26 into a constant-speed scanning beam and first reflecting mirrors 34 and 44, second reflecting mirrors 35 and 45 and third reflecting mirrors 36 and 46 for reflecting the constant-speed scanning beam and guiding the reflected beam to photosensitive drums (photoreceptors) 2a and 2b, with first and second openings 25a and 25b through which light passes being formed on the base 25. Each of light transmissive members 49 and 50 is fitted into the first and second openings 25a and 25b formed on the base 25.

Description

  The present invention relates to an optical scanning device for optically scanning a photoreceptor and an image forming apparatus such as a copying machine and a printer provided with the optical scanning device.

  In an image forming apparatus such as a copying machine or a printer, a photoconductor whose surface is uniformly charged by a charger is optically scanned by an optical scanning device, and an electrostatic latent image corresponding to image information is formed on the surface. . The electrostatic latent image is developed by a developing device using toner as a developer to be visualized as a toner image. The toner image is transferred onto a sheet by a transfer device and then heated and heated by a fixing device. A series of image forming operations is completed by discharging the sheet having the toner image fixed thereon by being pressed and fixed on the sheet.

  By the way, an optical scanning device that optically scans a photosensitive member to form an electrostatic latent image on a surface thereof includes a light source, a deflector that deflects a light beam emitted from the light source, and light deflected by the deflector. An imaging lens that converts the beam into constant speed scanning light, a folding mirror that folds the constant speed scanning light and guides it to the photoreceptor, and the like are housed in the housing.

  With regard to such an optical scanning device, for example, Patent Document 1 discloses a frame-like side wall that surrounds the housing and the periphery thereof in order to reduce the size and increase the strength while ensuring the required optical path length of the entire optical system of the optical scanning device. And a polygon mirror as a deflector at the center, and a plurality of optical components such as an imaging lens and a folding mirror are arranged in an upper and lower space cut by the base in the housing. A configuration is proposed.

JP 2002-148542 A

  By the way, in the optical scanning device proposed in Patent Document 1, optical components such as an imaging lens and a folding mirror are arranged separately in upper and lower spaces partitioned by the base in the housing. An opening for passing light is formed. If the opening is formed in the base in this way, the rigidity in the vicinity of the opening of the base is lowered, and the portion is more easily vibrated than other parts due to the influence of the vibration of the polygon mirror and the image forming apparatus. . Thus, if the vicinity of the opening of the base is likely to vibrate, the optical components arranged at positions sandwiching the opening of the base vibrate, and there is a problem that image degradation such as a jidder occurs.

  The present invention has been made in view of the above problems, and its object is to prevent a decrease in rigidity near the opening formed in the base of the housing and to suppress vibrations of optical components arranged on the base. An object of the present invention is to provide an optical scanning device and an image forming apparatus capable of preventing the occurrence of deterioration.

  In order to achieve the above object, according to a first aspect of the present invention, at least a light source, a deflector for deflecting a light beam emitted from the light source, and a deflector are provided in a housing whose interior is vertically partitioned by a base. An imaging lens that converts the deflected light beam into constant velocity scanning light and a folding mirror that folds the constant velocity scanning light and guides it to the photosensitive member are accommodated, and an opening for allowing light to pass through is formed in the base. In the optical scanning device, a light transmissive member is fitted into the opening formed in the base.

  According to a second aspect of the present invention, in the first aspect of the present invention, the light transmissive member is fitted into the opening by an interference fit.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the light transmissive member is formed of a parallel plate.

  An image forming apparatus according to a fourth aspect includes the optical scanning device according to any one of the first to third aspects.

  According to the present invention, since the light-transmitting member is fitted into the opening formed in the base of the housing, a reduction in rigidity due to the opening of the base is prevented, and the imaging lens and the folded lens disposed near the opening are prevented. Oscillation of optical components such as mirrors is suppressed, and image degradation such as jidder is prevented from occurring.

  Further, the productivity of the optical scanning device is enhanced by fitting the light transmissive member into the opening of the base by an interference fit.

1 is a side sectional view of an image forming apparatus (color laser printer) according to the present invention. It is a top view which shows the internal structure of the optical scanning device based on this invention. It is the sectional view on the AA line of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a cross-sectional view of a color laser printer as an embodiment of an image forming apparatus according to the present invention. The illustrated color laser printer is a tandem type, and a magenta image forming unit is provided at the center of the main body 100. 1M, a cyan image forming unit 1C, a yellow image forming unit 1Y, and a black image forming unit 1K are arranged in tandem at regular intervals.

  In each of the image forming units 1M, 1C, 1Y, and 1K, photosensitive drums 2a, 2b, 2c, and 2d, which are photosensitive members, are arranged, respectively, and around each of the photosensitive drums 2a to 2d, a charger 3a, 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Here, the photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving motor (not shown). The chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image, and each electrostatic latent image is visualized as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the driving roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The driving roller 8 is a secondary roller. The transfer unit is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the printer main body 100. It is installed.

  Further, below the image forming units 1M, 1C, 1Y, and 1K in the printer main body 100, two optical scanning devices 13 are arranged in parallel in the paper transport direction, and the printer main body below these optical scanning devices 13 is provided. A paper feed cassette 14 is detachably installed at the bottom of 100. A plurality of sheets of paper (not shown) are stacked and stored in the paper feed cassette 14. A pickup roller 15 for picking up paper from the paper feed cassette 14 and a picked up paper are located near the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for separating the toner and feeding them one by one to the transport path S.

  Further, the conveyance path S extending in the vertical direction on the side of the printer main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to a secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the transport path S, another transport path S ′ that is used when images are formed on both sides of the paper is formed. A plurality of reversing roller pairs 20 are appropriately used for the transport path S ′. Are provided at regular intervals.

  By the way, the conveyance path S arranged in the vertical direction on one side of the printer main body 100 extends to the paper discharge tray 21 provided on the upper surface of the printer main body 100, and the fixing device 22 and the discharge path are disposed in the middle. Paper roller pairs 23 and 24 are provided.

  Next, an image forming operation by the color laser printer having the above configuration will be described.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow (clockwise) in the image forming units 1M, 1C, 1Y, and 1K, and these photosensitive drums 2a. ˜2d are uniformly charged by the chargers 3a to 3d. Each optical scanning device 13 emits a light beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with each light beam, and each color on each photosensitive drum 2a to 2d. The electrostatic latent images corresponding to the color image signals are respectively formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is moved in the direction of the arrow in the figure by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied in the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 that is rotationally driven.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, in accordance with the timing at which the front end of the full-color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the drive roller 8 and the secondary transfer roller 10, The sheet fed to the transport path S by the feed roller 16 and the retard roller 17 is transported to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 and 24, and a series of image forming operations is completed. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

[Optical scanning device]
Next, the optical scanning device 13 according to the present invention will be described with reference to FIGS. 2 is a plan view showing the internal structure of one optical scanning device according to the present invention, and FIG. 3 is a cross-sectional view taken along line AA of FIG. Since the basic configuration of the two optical scanning devices 13 provided in the color laser printer shown in FIG. 1 is the same, only one optical device device 13 will be illustrated and described below.

  The optical scanning device 13 has a housing 25 integrally formed of resin. As shown in FIG. 3, the housing 25 has a horizontal base 25A that vertically divides the inside and a frame surrounding the periphery. The side wall 25B is formed in an H-shaped side section. A polygon mirror 26 serving as a deflector is disposed at the center of the upper surface of the base 25A of the housing 25, and the upper and lower spaces defined by the base 25A in the housing 25 are centered on the polygon mirror 26. Two scanning optical systems 30 and 40 are arranged symmetrically on both sides.

  The scanning optical systems 30 and 40 include laser diodes 31 and 41 which are light sources arranged on the upper surface of the base 25 </ b> A in the housing 25. Each laser diode 31 and 41 has a collimator lens (not shown) incorporated therein.

  Thus, the light beam L emitted from each of the laser diodes 31 and 41 is condensed into a linear light beam by a collimator lens (not shown), and then rotated to a polygon mirror 26 that is driven to rotate at a predetermined speed. Incident from two symmetrical directions. The light beams L incident on the polygon mirror 26 are deflected by the polygon mirror 26, and the scanning optical systems 30 and 40 are arranged along the traveling direction of the light beam L on the upper surface side of the base 25A. The first imaging lenses 32 and 42, the second imaging lenses 33 and 43, the first folding mirrors 34 and 44, and the second folding mirror 35 disposed along the traveling direction of the light beam L on the lower surface side of the base 25A. , 35 and third folding mirrors 36, 46, respectively.

  By the way, one optical scanning device 13 shown in FIGS. 2 and 3 exposes and scans the photosensitive drum 2a of the magenta image forming unit 1M and the photosensitive drum 2b of the cyan image forming unit 1C shown in FIG. On the optical path connecting the third folding mirrors 36 and 46 of the base 25A and the photosensitive drums 2a and 2b, and between the first imaging lenses 32 and 42 and the second imaging lenses 33 and 43, the main scanning direction ( The first rectangular opening 25a is formed in the left and right directions in FIG. 2, and is also in the main scanning direction on the optical path connecting the first folding mirrors 34 and 44 and the second folding mirrors 35 and 45 of the base 25A. Long rectangular second openings 25b are respectively formed.

  On the other hand, as shown in FIG. 2, each scanning optical system 30, 40 has a side next to the second imaging lenses 33, 43 on the base 25 </ b> A on which the polygon mirror 26 is disposed, and the polygon mirror 26 is the center. Synchronous detectors (BD sensors) 37 and 47 are respectively arranged at the point symmetry positions. These synchronization detectors 37 and 47 are arranged outside the effective scanning range of the photosensitive drums 2a and 2b by the light beam L, and by detecting the synchronization detection light beam L ′, the photosensitive drums by the light beam L. The start timing of exposure scanning (writing) onto 2a and 2b is determined.

  In each of the scanning optical systems 30 and 40, the light beam L ′ for synchronization detection is reflected on the lower surface of the base 25A and outside the effective scanning range (a point symmetrical position with the polygon mirror 26 as the center). Synchronous detection mirrors 38 and 48 for guiding to the synchronous detectors 37 and 47 are arranged, respectively.

  Thus, in the present embodiment, the first folding mirrors 34 and 44 and the second folding mirrors 35 and 45 are arranged in the middle of the synchronization detection optical path from the polygon mirror 26 to the synchronization detection mirrors 38 and 48, respectively. Has been. In addition, first imaging lenses 32 and 42 and second imaging lenses 33 and 43 are disposed in the middle of the synchronization detection optical path from the polygon mirror 26 to the first folding mirrors 34 and 44, respectively.

  By the way, in the present embodiment, the first opening 25a and the second opening 25b respectively formed on the base 25A for the respective scanning optical systems 30 and 40 are provided with the opening 25a and the second opening. Light transmissive members 49 and 50 made of a long and narrow rectangular parallel plate having the shape of the portion 25b are respectively fitted by interference fitting.

  Next, the operation of the optical scanning device 13 configured as described above will be described.

  The light beam L emitted from the laser diodes 31 and 41 provided in the respective scanning optical systems 30 and 40 in one optical scanning device 13 is condensed into a linear light beam by a collimator lens (not shown), and The light enters the polygon mirror 26 that is rotationally driven at a predetermined speed from two symmetrical directions.

  As described above, each light beam L incident on the polygon mirror 26 is deflected by the polygon mirror 26 and then passes through the first imaging lenses 32 and 42 and the second imaging lenses 33 and 43 so as to perform constant velocity scanning. It is converted into light L. The constant-speed scanning light L is folded downward at a right angle by the first folding mirrors 34 and 44, passes through the second opening 25b formed in the base 25A, and the second folding mirrors 35 and 45. The second folding mirrors 35 and 45 are folded at a right angle and proceed horizontally along the lower surface of the substrate 25A. Thereafter, the light beam L is folded upward at a right angle by the third folding mirrors 36 and 46, passes through the first opening 25a formed in the substrate 25A, toward the photosensitive drums 2a and 2b, and these photosensitive drums 2a. , 2b are exposed and scanned.

  2 and FIG. 3 performs exposure scanning on the photosensitive drum 2a of the magenta image forming unit 1M and the photosensitive drum 2b of the cyan image forming unit 1C shown in FIG. The color laser printer shown in FIG. 1 is provided with two similar optical scanning devices 13 arranged side by side, and these two optical scanning devices 13 use the photosensitive drums 2c of the other yellow image forming unit 1Y and Bralac image forming unit 1K. , 2d, all of the four photosensitive drums 2a to 2d are exposed and scanned by the light beam L.

  The synchronous detection light beam L ′ deflected by the polygon mirror 26 is narrowed by passing through the first imaging lenses 32 and 42 and the second imaging lenses 33 and 43, and then the first folding mirror. 34 and 44 are folded downward at a right angle, pass through a second opening 25b formed in the base 25A, reach the second folding mirrors 35 and 45, and are folded at a right angle by the second folding mirrors 35 and 45. Then, it proceeds horizontally along the lower surface of the substrate 25A and reaches the synchronization detection mirrors 38 and 48. Thereafter, the light beam L ′ is reflected by the synchronization detection mirrors 38 and 48 and reaches the second folding mirrors 35 and 45, and is reflected again by the second folding mirrors 35 and 45, and is folded upward at a right angle, thereby returning the base 25A. Passing through the second opening 25b formed on the first and second mirrors 34 and 44 again.

  The light beam L ′ is folded at a right angle by the first folding mirrors 34 and 44, travels in parallel along the upper surface of the base 25 A and is guided to the synchronization detectors 37 and 47. As a result, the timing for starting exposure scanning (writing) onto the photosensitive drums 2a and 2b by the light beam L is determined as described above. In this embodiment, as shown in FIG. 3, the length of the synchronization detection optical path from the polygon mirror 26 to the synchronization detectors 37 and 47 is set to the length of the scanning optical path from the polygon mirror 26 to the photosensitive drums 2a and 2b. It is set approximately equal to the length.

  By the way, in the present embodiment, as described above, the first opening 25a and the second opening 25b formed on the base 25A of the housing 25 for the respective scanning optical systems 30 and 40 are light transmissive. Since the members 49 and 50 are fitted, respectively, the rigidity of the base 25 is prevented from being lowered by the first and second openings 25a and 25b, and is arranged in the vicinity of the first and second openings 25a and 25b. Vibrations of optical components such as the first imaging lenses 32 and 42, the second imaging lenses 33 and 43, the first folding mirrors 34 and 44, the second folding mirrors 35 and 45, and the third folding mirrors 36 and 46 are suppressed. The For this reason, image quality such as judder does not occur in the color image formed by the color laser printer shown in FIG. 1, and a high-quality color image can be stably obtained.

  In the present embodiment, the light transmitting members 49 and 50 are fitted into the first and second openings 25a and 25b of the base 25 by interference fitting, so that the productivity of the optical scanning device 13 is improved. The effect that it is raised is also acquired.

  In the above, the embodiment in which the present invention is applied to the color laser printer and the optical scanning device provided in the color laser printer has been described. However, the present invention is provided in any other image forming apparatus other than the color printer and the image forming apparatus. Of course, the present invention can be similarly applied to the optical scanning device.

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum (photoconductor)
3a to 3d charger 4a to 4d developing device 5a to 5d transfer roller 6a to 6d drum cleaning device 7 intermediate transfer belt 8 drive roller 9 tension roller 10 secondary transfer roller 11 belt cleaning device 12a to 12d toner container 13 optical scanning device 14 Paper cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Transport roller pair 19 Registration roller pair 20 Transport roller pair 21 Paper discharge tray 22 Fixing device 23, 24 Paper discharge roller pair 25 Housing 25A Housing base 25B Housing side wall 25a Housing First opening portion 25b Second opening portion of housing 26 Polygon mirror (deflector)
30, 40 Scanning optical system 31, 41 Laser diode (light source)
32, 42 First imaging lens 33, 43 Second imaging lens 34, 44 First folding mirror 35, 45 Second folding mirror 36, 46 Third folding mirror 37, 47 Third reflection mirror 38, 48 Synchronous detector 37, 47 Sync detection mirror 49, 50 Light transmissive member L, L 'Light beam S, S'

Claims (4)

At least a light source, a deflector that deflects a light beam emitted from the light source, and an image that converts the light beam deflected by the deflector into constant-speed scanning light in a housing whose interior is partitioned vertically by a base In an optical scanning device that houses a lens and a folding mirror that folds constant-speed scanning light and guides it to the photoreceptor, and forms an opening through which light passes.
An optical scanning device, wherein a light transmissive member is fitted into the opening formed in the base.   The optical scanning device according to claim 1, wherein the light transmissive member is fitted into the opening by an interference fit.   3. The optical scanning device according to claim 1, wherein the light transmissive member is formed of a parallel plate. An image forming apparatus comprising the optical scanning device according to claim 1.

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